1. Field of the Invention
The present invention relates to a rotation number control device for a disk signal reproduction apparatus that reproduces information using a disk-like recording medium on which the information is recorded along a spiral track, such as an optical disk or a magnetic disk.
2. Description of the Related Art
In a conventional apparatus, preferably, an information signal on a disk-like recording medium such as an optical disk or a magnetic disk is read out at a speed which is as high as possible. In such a conventional apparatus, when a disk is rotated at a high speed, undesired vibration of a spindle motor causes mechanical vibration, so that the information signal on the disk is erroneously read out or on occasion cannot be read. In order to solve this problem, Japanese Patent Unexamined Publication No. Hei. 7-184386 discloses a technique in which xe2x80x9cvibration of a spindle motor is directly or indirectly detected, and the driving waveform of the spindle motor is corrected on the basis of the detected vibration, thereby suppressing the vibration of the spindle motorxe2x80x9d (column 0009 of the publication), and a technique in which xe2x80x9cthe driving waveform of a spindle motor is corrected, thereby suppressing the vibration of the spindle motor, and also a driving signal of a recording/reproducing head is corrected on the basis of the vibration of the spindle motorxe2x80x9d (column 0012 of the publication). Further, Japanese Patent Unexamined Publication No. Hei. 8-106714 discloses xe2x80x9ca spindle motor driving device in which mechanical vibration produced by a spindle motor when the spindle motor is adjusted into a predetermined rotation number is reduced, deviation out of focus and tracking servo controls is prevented from occurring, and the operation of adjustment into the predetermined rotation number is surely conductedxe2x80x9d (column 0016 of the publication).
In such a conventional device, when a certain standard disk is mounted, undesired vibration of a spindle motor causes mechanical vibration as the rotation number of the disk becomes higher, and therefore a technique of solving this problem is disclosed. However, in each actual disk such as a music disk or a CD-ROM disk, the vibration state of the disk is varied by deviation in the position of the center hole, the thickness, and the mass eccentricity of the disk.
Further, the rotation number at which such vibration starts to occur is dispersed depending on individual disks. Each time when a disk is replaced with another one, therefore, the rotation number at which vibration starts to occur must be detected for each disk. However, any countermeasure for the above is not taken in the conventional device.
The invention has been made in order to solve the above-discussed problems. Depending on individual disks, the vibration state of a disk is varied by deviation in the position of the center hole, the thickness, and the mass eccentricity of the disk, and the rotation number at which such vibration starts to occur is dispersed. Therefore, it is an object of the invention to provide a rotation number control device in which, each time when a disk is replaced with another one, the rotation number at which vibration starts to occur is detected for each disk, the rotation number of the disk at a time when maximum vibration in a disk allowable vibration range is produced, is set as a maximum allowable rotation number, and the rotation number of the disk is controlled so as not to exceed the maximum allowable rotation number for each disk.
In order to achieve the above object, according to a first aspect of the invention, there is provided a rotation number control device for a disk signal reproduction apparatus, comprising: a disk drive unit that rotates a disk on which information is recorded along a spiral track; a rotation number detection unit which detects a rotation number of the disk; a rotation number control unit which controls the rotation number of the disk rotated by the disk drive unit; a vibration detection unit which detects vibration of the disk or a spindle motor and due to rotation of the disk; and a rotation number storage unit which, for each disk, stores a rotation number of the disk at a time when maximum vibration in a disk allowable vibration range is produced during rotational acceleration of the disk, as a maximum allowable rotation number, wherein the rotation number of the disk is controlled so as not to exceed the maximum allowable rotation number of the disk which is stored in the rotation number storage unit.
According to a second aspect of the invention, there is provided a rotation number control device for a disk signal reproduction apparatus, comprising: a disk drive unit that rotates a disk on which information is recorded along a spiral track; a rotation number detection unit which detects a rotation number of the disk; a rotation number control unit which controls the rotation number of the disk rotated by the disk drive unit; a vibration detection unit which detects vibration of the disk or a spindle motor and due to rotation of the disk; a rotation number storage unit which, for each disk, stores a rotation number of the disk at a time when maximum vibration in a disk allowable vibration range is produced during rotational acceleration of the disk, as a maximum allowable rotation number; and a central processing unit which receives an output of the rotation number storage unit, a detection output of the rotation number detection unit, and a detection output of the vibration detection unit, wherein the rotation number of the disk is controlled so as not to exceed the maximum allowable rotation number of the disk which is stored in the rotation number storage unit, by the central processing unit.